The invention relates to a wheeled motor vehicle provided with a control device for regulating the longitudinal dynamics of the vehicle, such as speed, for example.
Traditionally, a motor vehicle using an automatic transmission system to control its speed operates by increasing the engine fuel supply for uphill control, and using the engine brake for downhill control.
It is well known that, for a fixed transmission ratio, the engine brake control capability going downhill is very limited compared to the uphill control, and that the only degree of freedom, which consists in changing the transmission ratio of the gearbox, in the case of a controlled gearbox, has inconveniences, such as the noise produced by increasing the engine speed, and jolting during a change in the transmission ratio.
It is also known that the wheel brakes must be used only in certain instances to assist the engine brake, and that such an action does not ensure smooth control of the vehicle speed going downhill, either.